The present invention relates to the art of recovering test gases after they are used to test a sample holder for leaks. It finds particular application in recovering helium.
The use of helium is especially suited as the test gas, although the invention can be used with various other test gases. Helium is supplied to a test chamber until the helium fills a testing area.
To test a workpiece, such as a sample holder, for leaks a differential pressure is created across a workpiece. The test gas diffuses from the side having the higher pressure and to the side with the lower pressure. Any leaks are detected using a gas detector or sensor.
In the past, there have been two methods used to test for leaks in sample holders. In the first method, the sample holder is placed in a testing chamber or hood. Then, either the sample holder interior or test chamber is filled with helium. A test gas detector, i.e., a mass spectrometer, is connected to measure the inside of one or the other of the test chamber or the sample holder. If the sample holder contains holes allowing leakage, the leaking helium is detected by the mass spectrometer. Otherwise, if there is no leak, nothing is detectable.
In the second known method, the sample holder is filled with helium. Then, a leakage evaluation is performed by passing the probe of a leak detector over the outside surface of the sample holder.
In these prior art devices, the test gas which is used to determine if there are leaks in the sample holder permits sample gas to escape into the atmosphere.
Further, the helium supply unit connected to the sample holder or hood is basically only a helium supply. These procedures are quite costly because helium is very expensive as a test gas to have it all escape during testing. Also, there is a danger that the helium which escapes can be detected and result in false or erroneous results during any future or simultaneous leakage testing.
The present invention contemplates a new and improved apparatus and method which overcomes the above-referenced problems and others and provides a testing apparatus which recovers and reuses the test gas.